In January 1978, two guys from Chicago, Ward Christensen and Randy Suess, decided to devise a simple communication system between two computers, through a telephone line. They used the first generation of 110-baud Hayes modems that appeared first en April 1977.
Christensen, who wrote the first binary file transfer protocol in August 1977 (MODEM.ASM, then XMODEM), developed the software, and Suess designed the hardware.

One month later, their system was running. They called it the Computerized Bulletin Board System (CBBS). After several months of tests and improvements, CBBS finally went online to the public in 1979. It was the first electronic message-posting network (except time sharing systems) where participants could post messages to a public "board", read and respond to other ones and thus participate to virtual discussions.
Few months later, virtual bulletin boards began popping up around the country, mainly intended to computer hobbyists and scientists.

At the first time, BBSs were painfully slow as the transmission speed didn't exceed 300 bauds (30 to 40 chars. per sec.). Only ASCII codes and ANSI escape sequences were used. Later, when 1200 and 2400 baud modems were launched, the speed became acceptable.

BBSs were very popular during the 80s and early 90s. They greatly declined in popularity when commercial Internet access became common. However, they were in many ways a precursor to the modern form of the World Wide Web and many aspects of the Internet.

M. Simon, who designed the S-100 I/O board used in the world's first BBS, adds:

When I had a shop on Chicago on 2053 N. Sheffield they came over all the time to get advice on how to get the Master I/O Board up and running. I used the 8251 serial chip and there was no way other than a hard reset to determine the state of the chip. I think they did a cut and a jump on the board to the on board 8255 for a hardware reset.

They told me what they were planning and I wondered why any one would do something so crazy!

I made one or two visits to their basement to help out and see what was going on. We all belonged to the CACHE club in those days. Chicago Area Computer Hobbyist Exchange. My wife silk screened bumper stickers for the club. We also sold T-shirts with "Support the Revolution, Buy a Computer" for a slogan.